Mathias et al. U.S. Pat. No. 5,330,464 discloses a breakable seal located within a fluid path. The seal comprises a rigid, break-apart plastic cannula member, which lays within a flexible plastic housing. Mathias '464 disclose projections on both the front and back ends of the cannula member, which engage the wall of the flexible housing to restrain the cannula member, once broken, from moving inside the housing.
Frangible seals of the type shown in Mathias '464 are widely used in association with multiple blood bag systems. These systems undergo centrifugation during normal use. During centrifugation, the flexible housing, which encloses the cannula member, can bend about the front end of the cannula member. Exposed to centrifugal forces, the projections on the front end of the cannula member can penetrate and even puncture the plastic walls of the housing.